supplementary materials

Bis[O-methyl (4-ethoxyphenyl)dithiophosphonato-2S,S']nickel(II)

In the title compound, [Ni(C9H12O2PS2)2], the NiII atom resides on an inversion center and is coordinated by four S atoms [Ni-S = 2.2328 (4) and 2.2455 (3) Å] in a distorted square-planar geometry [S-Ni-S = 88.443 (13) and 91.557 (13)°]. In the crystal, molecules related by translation in [110] are linked into chains via weak C-HO interactions. The crystal packing exhibits short intermolecular SS contacts of 3.3366 (5) Å.

The phosphor-1,1-dithiolate class of compounds is the heavier and softer
congener of the popular phosphonate derivatives. It contains the S2P
functionality as a common feature and several sub-categories are known which
include the dithiophosphato [S2P(OR)2]¯, (R = typically alkyl),
dithiophosphinato [S2PR2]¯ (R = alkyl or aryl), and
dithiophosphonato [S2PR(OR')]¯, (R = typically aryl or ferrocenyl,
R' = alkyl) monoanionic ligands. The latter may be described as a
hybrid of the former two, and are also much less developed. Amongst all metals
involved in the coordination chemistry of dithiophosphonato ligands, however,
nickel(II) is by far the best represented (Van Zyl & Woollins, 2012)
with the
first X-ray structural report of a nickel(II) dithiophosphonate complex
reported more than four decades ago (Hartung, 1967).
The title complex, (I), was formed from the
reaction between NiCl2.6H20 and the ammonium salt of
[S2P(OMe)(4-C6H4OEt)] (molar ratio 1:2) in an aqueous/methanolic
solution, the NH4Cl by-product was dissolved and the precipitated product
filtered off and washed with water. General and convenient methods to prepare
dithiophosphonate salt derivatives have been reported (Van Zyl & Fackler,
2000).

A colorless methanol (40 ml) solution of NH4[S2P(OMe)(4-C6H4OEt)] (1.044 g, 4.474 mmol) was prepared. A second green solution of NiCl2.6H20 (540 mg, 2.272 mmol) in deionized water (20 ml) was prepared, and added to the
colorless solution with stirring over a period of 5 min. This resulted in a
purple precipitate indicating the formation of the title complex. The
precipitate was collected by vacuum filtration, washed with water (3 x
10 ml) and allowed to dry under vacuum for a period of 3 hrs, yielding a dry,
free-flowing purple powder. Purple crystals suitable for X-ray analysis were
grown by the slow diffusion of hexane into a dichloromethane solution of the
title complex. Yield: 1.004 g, 41%. M.p. 168°C.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger.